Planetary nebulae are expanding shells of gas and dust that have been ejected from a star during the process of its evolution from main sequence star into a red giant or white dwarf. They are relatively rare, but important for astronomers studying the chemical evolution of stars and galaxies. ...
Language learning shapes your brain into a well-oiled multi-tasking machine. As you build a new mental word list, you'll notice an improvement in your ability to do several things at once and to quickly switch between tasks.【4】So, start by determining what you want to do -taking a ...